After my last carb icing June 20. (90% humitiy, dew & temp less than 2 degrees C) This is the third time I have had it happen and the second time I had to land.

I added a glow plug in the inlet of the carburetor it draws about 10 amps. Running the engine at 1,500 rpm for 30 seconds the carburetor was warm. At full power 30 seconds still warm. I think this will help.

Another thing i notice on the pictures is the "throttlespring"- I´ve been meaning to do that too for some time. I actually think that is an important mod, the throttle wire "pushes" the throttle and it will bend at the end which makes it prone to breaking from fatigue. Someone already soldered the wire on XST to reinforce it... If however the wire breaks it will be no sweat if you have that spring- you get full throttle and can "blip" (cut the ignition repeatedly to reduce rpm´s, just like they did with old rotary engines) your way down if you need to. And best of it all- you can do that mod without having to drill holes in your precious, threatened by extinction Zenith carburator......

Take 5(b) just 4 fun/ Jörgen, SE-UDI, SE-XST

Donald

Having your engine quit will get you nervous. My battery is a 17amp Gell cell. The carb heat has only been install for a week. I mainly have as back up. The times I have carb ice is long taxi times and low power settings in humid weather. I plan on using it for maybe for the last 30-60 seconds of taxing before take off and as needed in flight. For in flight icing I think it will clear the ice fairly fast, Then I will fly at a higher power setting (3000rpm +)

Collin

I've had mine quit 3 times but not from carb ice. It sure gets your attention!
I thought you were going to tell us about your power generator but instead you have power storage.

@ Sam,

You're going to get a lot of questions about your carb set up. The original Zenith is a worry for a lot of people, so maybe start getting together photos and a parts list.

Quote:

Originally posted by Collin I plan on using it for maybe for the last 30-60 seconds of taxing before take off and as needed in flight. For in flight icing I think it will clear the ice fairly fast, Then I will fly at a higher power setting (3000rpm +)

Just a couple of questions. As a normal glow plug heats up to 800º C - over 1400º F - how safe is it to fit one in a carb? Just a small fume of gas and your little bird will blow up to the next galaxy. The second question concerns power. If you heat the carb prior to takeoff, the plug stays hot for a while and you can't get the max power out of engine when most needed. So, how does that effect?

I may be wrong, but am afraid being quite not...

-A-

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***** Antti Laukkanen, Helsinki, Finland - RF4D OH-371 - RF4D OH-370 - RF5 OH-386 *****

The heating element is forward of the carburetor inlet so the fuel stand off is not directly on the element. With the engine running at a higher power settings the element is being cooled, so not as hot as if it was in a diesel pre camber.

My charging system for now is a VW/Audi solar panel. It fits upright in the baggage area. Output is only 275ma. But if parked at a fly-in for a day or so the battery gets charged. They can be found on ebay for $30-40. The size is 48cmx28cm.

I will add a charging system soon.

This is the 1000th post on the forum. Thanks Steve for setting it up.

Just a quick carb heat update. My ele. carb heat has been installed 1 1/2 months. I have been using it just before take off when dew/air temps are close and use it on down wind.

I went for a flight early this morning before my household became a zoo. After flying for a 1 1/2 hours and on decent the engine started running rough. I flipped the carb heat on and about 30 seconds later the engine ran smooth and the power was back.

Collin

As per Jorgen’s suggestion, moving my carby ice question across from this thread:

http://sbeaver.com/cgi-bin/fournier/cutecast.pl?session=7K5YgdbjEH9jLtF9kU7YuQnrBL&forum=13&thread=253&page=1

Thanks Bob and Jorgen, your feedback confirms what I thought. The notion in the German CFI news letter referred to the 1400 and the original Zenith. With the increase in gas velocity in the venturi one would expect a lower inlet temperature.

A very good reminder to watch prolonged taxi times at low throttle settings. The new location for my Fournier has long runways, i.e. long taxiways…

Thanks again.

BR

Tim

That one time I got icing, I had anticipated it, and as soon as I heard the engine begin to falter, I vigorously opened and closed the throttle a couple of times (to break off any ice build-up on the throttle butterfly), and then accelerated at full power for a minute or so to let the heat build up in the cylinders & heads, so the air in the lower cowling would become warm again.
Then it went away.
Then I landed, keeping on a trickle of power against extended spoilers around the pattern.

I hope that it is obvious to everybody that, for the standard Fournier carb heat to work properly, especially at low powers, the cowlings and baffles must seal perfectly -- see the engine upgrade/cooling thread, or search for 'cooling'

This is probably the best thread
http://sbeaver.com/cgi-bin/fournier/cutecast.pl?session=7QweYW8j4ku7llAxARoqXRIuiX&forum=13&thread=284

Also there is some information on making new baffles here
http://sbeaver.com/cgi-bin/fournier/cutecast.pl?session=cDF7QqhOq8KpkodhtUoKrmfL5d&forum=13&thread=683

I know I keep going on and on about cooling, but it seems to be the worst aspect of maintenance on many RF4s.
Forget oil coolers, they only lower the viscosity of your lubricant.

The most important thing is to get rid of the heat from your heads and barrels (and use it to heat your carburetor).
This means the all the baffles must seal perfectly.
The most important seals are those between the vertical baffles and the upper cowling.
Have you checked yours recently? Will they allow any air to squeeze past when you are in the air and your upper cowl is lifted by the air pressure plus incoming airflow blows them back.

Next most important are the seals between horizontal baffles and head and cylinder fins.
Airflow will always take the easiest route from your upper cowling to your lower cowling, and forcing it past the fins is the most difficult route, so it will bypass wherever it can.

I took a look into the engines of all the Fourniers at Gap-Tallard, and they were nearly all dreadful, with great, gaping gaps between the baffles and the fins and the baffles and the cowlings.

Any tiny bit of cool air that gets into your lower cowling will reduce the carb inlet air temperature and increase your risk of carb ice.

Any tiny bit of cool air that misses your head and cylinder fins will increase your head temperatures and increase the risk of a broken valve.

It is a great shame that so many glider pilots seem to hate their engines and don't care for them properly.
I don't mind them killing themselves, that is simple Darwinian selection, but do they have to take one of our lovely Fourniers with them?

Yours, Bob

The cost to make it right is low compared to the benefits of reliability, safety, longer engine parts life etc
so its a mystery why it is so often overlooked.

I think that us folks in the hotter climates are more acutely aware of these heat issues.

The folks in the cooler climates can perhaps get by with less than optimal baffling/sealing,
but when it comes to carb ice all bets are off and the European climate is ideal for incidents
of carb ice in improperly sealed cowls.

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Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Quote:

It is a great shame that so many glider pilots seem to hate their engines and don't care for them properly. I don't mind them killing themselves, that is simple Darwinian selection, but do they have to take one of our lovely Fourniers with them?

I had to clean the coffee off the screen after that, Bob. I have to admit I feel guilty as charged so maybe I´m more of a glider pilot then. I think you have a valid point too Ray that when you don't regularly have to worry about overheating you are probably not as careful with your cooling as you should. To my defence I have to say that baffles are a real pest when you try to get to different parts of the engine, and more than once I´ve found that the baffles fitted (even) less well after tinkering with something on the engine. Evidently some baffle-mounting solutions are better than others and more or less easy to take on and off. So maybe a new thread with pictures of different solutions for seating baffles properly?

May the 4's be with you/ Jörgen

Just another idea for a lower powered carb heater that would perhaps not have the instant effect of a glow plug but would heat the carb housing and use less power.

I also had an Austin Marina sedan many years ago and it had a heater element strap that was secured to the outside of the carb, much like a pipe clamp and also heated the carb body quite effectively.

Just a few ideas as an alternative to a glowing plug.

I'd be concerned about a glow plug igniting fuel at the entrance to the carb should it become flooded.

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Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org